Desperate to help their autistic children, hundreds of parents nationwide are turning to an unproven and potentially damaging treatment: multiple high doses of a drug sometimes used to chemically castrate sex offenders.

The therapy is based on a theory, unsupported by mainstream medicine, that autism is caused by a harmful link between mercury and testosterone. Children with autism have too much of the hormone, according to the theory, and a drug called Lupron can fix that.

"Lupron is the miracle drug," Dr. Mark Geier of Maryland said after meeting with an autistic patient in suburban Chicago.

Geier and his son developed the "Lupron protocol" for autism and are marketing it across the country, opening clinics in states from Washington to New Jersey. In the Chicago area, the treatment is available through Dr. Mayer Eisenstein, a family practitioner in Rolling Meadows.

But experts say the idea that Lupron can work miracles for children with autism is not grounded in scientific evidence.

Four of the world's top pediatric endocrinologists told the Tribune that the Lupron protocol is baseless, supported only by junk science. More than two dozen prominent endocrinologists dismissed the treatment earlier this year in a paper published online by the journal Pediatrics.

Simon Baron-Cohen, a professor of developmental psychopathology at the University of Cambridge in England and director of the Autism Research Center in Cambridge, said it is irresponsible to treat autistic children with Lupron.

"The idea of using it with vulnerable children with autism, who do not have a life-threatening disease and pose no danger to anyone, without a careful trial to determine the unwanted side effects or indeed any benefits, fills me with horror," he said.

Experts in childhood hormones warn that Lupron can disrupt normal development, interfering with natural puberty and potentially putting children's heart and bones at risk. The treatment also means subjecting children to daily injections, including painful shots deep into muscle every other week.

This weekend, Eisenstein, Geier and his son, David, are scheduled to speak at the Autism One conference at the Westin O'Hare in Rosemont. The five-day conference, featuring a keynote speech by actress-turned-activist Jenny McCarthy, steps in where modern medicine has yet to succeed, offering answers for what causes autism and treatments with allegedly dramatic results.

All three men plan to talk about the link they see between autism and vaccines; the Geiers will also discuss hormones and autism.

Mark Geier and Eisenstein are physicians, but neither is board-certified in any specialty relevant to autism and the use of Lupron, including pediatrics, endocrinology, psychiatry and neurology. Geier is a geneticist; his son has a bachelor's degree in biology. Eisenstein, a family doctor who preaches a message of home birth, vitamins and vaccine safety, said he treated "virtually no" autistic children in the past.

Eisenstein said he met the Geiers last summer at the Health Freedom Expo in Chicago and that he began offering Lupron in his office because parents of autistic children were pleading with him for help.

Since his Autism Recovery Clinic opened in late January, Eisenstein said he has seen about 75 autistic children, with about 35 undergoing extensive lab testing. On May 11 he told the Tribune that four or five children were on Lupron, and 15 to 20 could start treatment within weeks.

The Geiers say they have probably treated 300 autistic children and a handful of adults with Lupron, and an additional 200 people are being tested.

In February, when the Geiers visited his office, Eisenstein was effusively enthusiastic about Lupron. "It is awesome, just awesome," he told doctors in his practice after the Geiers spoke about their therapy.

But three days after his May interview with the Tribune, Eisenstein called to say he was having second thoughts about the autism clinic, citing issues with insurance companies and less-than-spectacular results.

"It's highly unlikely that we're going to be part of the autism program much longer," Eisenstein said. "I'm not pleased enough with it. It's not where I want to put my energy."